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FEEDING FOR MILK COMPOSITION. José Eduardo Portela Santos VMTRC – UC Davis. Milk Components. Fat Content Fatty acid profile Crude protein Content True protein vs NPN Lactose Minerals and vitamins. Several nutritional factors affect the composition of milk of dairy cows:

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FEEDING FOR MILK COMPOSITION

José Eduardo Portela Santos

VMTRC – UC Davis


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Milk Components

  • Fat

    • Content

    • Fatty acid profile

  • Crude protein

    • Content

    • True protein vs NPN

  • Lactose

  • Minerals and vitamins


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  • Several nutritional factors affect the composition of milk of dairy cows:

    • Energy intake (Mcal of NEL)

    • Energy source

      • CHO

      • Lipids

    • Protein intake

    • Protein degradability and quality

    • Interactions between protein and energy

    • Amino acids

    • Minerals: Na, K (DCAD)

    • Feed additives (Niacin, fibrolytic enzymes)


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Milk Fat of dairy cows:

  • Forage:Concentrate ratio

  • CHO:

    • NDF

    • Effective NDF

    • Physically effective NDF

    • Ruminal digestibility of NDF

    • NFC

      • Composition of the NFC: sugars, starch and pectin

      • Ruminal degradability of starch


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  • Ionophores of dairy cows:

  • Fat supplementation

  • Lack of RDP (fiber digestibility and buffering effect)

  • Dietary buffers


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Theories of dairy cows:

  • Low fat diets

  • Acetate deficiency

  • B-OH-butyrate deficiency

  • High rumen molar concentration of propionate: Insulin theory (glucogenic theory)

  • Vit. B12 deficiency

  • Trans fatty acids


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Mechanism of Action of of dairy cows:Trans FA

  • Milk fat suppression: reduced SCFA (De Novo synthesis)

  • Trans fatty acids depress milk fat in 48 to 72 hs

  • Preliminary data from Maryland (Piperova et al., 1998):

    • Acetil CoA Carboxylase activity decreased (61%)

    • Fatty acid synthase activity decreased (54%)

    • Acetil CoA Carboxylase mRNA decreased (55%)


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Nutritional Causes of Milk Fat Suppression of dairy cows:

  • Inadequate NDF

  • Inadequate physically effective NDF (particle size)

  • Poor NDF digestibility

  • Forage source: buffering capacity

  • Excessive amounts of NFC

  • Excessive amounts of RDS

  • High fat diets


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  • Fat sources with highly unsaturated FA profile of dairy cows:

    • Yellow grease, oils

  • Interactions between fat source and forage source (binding sites)

    • Alfalfa hay vs corn silage

  • Protein supplements with high PUFA content

    • Fish meal, blends of marine by products

  • Lack of RDP (fiber digestibility & buffer effect)

  • Lack of buffers


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Milk Protein of dairy cows:

  • NEL intake

  • Forage:Concentrate ratio

  • Amount of fermentable CHO (RDS)

  • Dietary CP level

  • Amino acid profile of the protein flowing to the duodenum

  • Dietary fat


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Effect of Grain Processing on Plasma Insulin of dairy cows:

P < 0.05

  • Data from 832 blood samples from 32 cows (Santos et al., 2000)


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Dietary Protein and Milk Protein of dairy cows:

  • Low efficiency of N utilization for milk protein synthesis (< 30%)

  • Sprndly (1986): No relationship between dietary CP content and milk protein concentration

  • Emery (1978): correlation between dietary CP and milk protein content (r2=0.35)

    • The effect of higher CP diet is associated with greater DMI and total energy intake


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Dietary Fat and Milk Protein of dairy cows:

  • Negative relationship between dietary fat and milk protein concentration

  • Independent of fat source

  • Increased efficiency of amino acid extraction

  • Supplying more fermentable CHO or high quality RUP partially overcomes milk protein depression


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Conclusions of dairy cows:


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